This page covers a second sand-cast leaded gunmetal listed under the C83600 reference, distinct from the standard 85-5-5-5 grade covered elsewhere in this library. Its underlying specification data points to a lower-tin variant of the leaded red brass family — DIN CuSn2ZnPb (Werkstoffnummer 2.1098) rather than the 5%-tin CuSn5ZnPb (Rg5) that defines classic C83600. The tin content here runs closer to 2%, with correspondingly higher zinc, which shifts the alloy slightly toward the leaded semi-red brass end of the gunmetal family (a composition region closer to what's registered as UNS C83450 in the copper alloy system).

In practice this alloy is used interchangeably with standard gunmetal for general-purpose plumbing fittings, valve bodies, and low-to-moderate pressure hardware, since the lower tin content trades a small amount of strength and dezincification resistance for lower raw-material cost. The lead content stays in the same functional range as standard C83600, so machinability and bearing-surface behavior are very similar; the difference shows up mainly in mechanical properties and corrosion performance in more demanding service. Keep this page separate from the standard C83600 grade when specifying material for pressure-critical or marine applications, and confirm the exact certificate composition with your foundry.

Machinability behavior in this lower-tin variant tracks closely with standard C83600, because the mechanism driving easy chip formation is the lead content, not the tin. The 4-6% lead is present as fine, insoluble particles throughout the copper-zinc-tin matrix, and those particles shear ahead of the tool tip to snap the chip into short segments while laying down a thin, friction-reducing film at the cutting interface.

With slightly less tin and more zinc in the mix, this alloy tends to run a touch softer than the standard 5%-tin grade, which if anything makes chip control marginally easier and cutting forces marginally lower, though the difference is modest in day-to-day shop practice. Surface finish and tool life both remain strong for the same reasons as standard gunmetal: minimal built-up edge, low abrasiveness, and a self-lubricating cut. The usual sand-casting caveats still apply — watch for porosity in heavier sections and a harder as-cast skin on the first pass.

As with all leaded copper casting alloys, this material sits well above lead-free bronzes and brasses on the machinability scale, though it doesn't quite reach the 100% benchmark set by wrought C36000 free-cutting brass, whose fine-grained bar structure and slightly higher lead loading give it an edge over any sand casting.